1. Field of the Invention
The invention relates to an optical rotating data transmission system such as a rotary joint for transmitting optical signals between units rotatable relative to each other. Systems of this kind are preferably used in computer tomographs. The invention also relates to a method for cleaning a surface of the optical transmission system.
2. Description of the Related Art
For transmission of optical signals between units rotatable relative to each other, various systems are known, in particular systems having an unobstructed diameter. With these, a basic problem exists of designing a means for conveying light along the circumference of the system, and also suitable means for coupling light in and out. For use in computer tomographs, systems of this kind must have large unobstructed diameters of the order of magnitude of 1 meter. During rotation, the circumferential speed may be of an order of magnitude of 20 m/s. At the same time, data rates of more than 1 gigabyte per second (Gbaud) should be possible.
Nearly all kinds of optical rotating data transmission systems react sensitively to contamination in the region of the optical signal path. Even in relatively clean surroundings in which, for example, computer tomographs are used, dust particles occur. Thus, for example, in computer tomographs, usually a slip-ring having a brass track and carbon brushes running thereon is used for supplying power supply to an X-ray tube. During operation, these carbon brushes become abraded by sliding on the brass track and thus produce an extremely fine dust that can penetrate into even the smallest of openings. Contamination on the light guide can lead to a high attenuation of signals or an interference with transmission.
A system for wideband signal transmission by means of a light guide divided along a longitudinal direction is disclosed in WO 03/069392. The contents of WO 03/069392 are incorporated in the present document by reference. Here the light guide is exposed and thus unprotected from dust and other contamination.